This invention relates to a waterproofing construction and method for tunnels, and more particularly to the constructions and use of a vulcanization-type rubber film on a tunnel waterproofing surface.
In this invention, paste, mortar, and concrete are used as general terms to refer to cement concrete.
The principle tunnel construction method in Japan currently is the New Austrian Tunneling Method (NATM method). In the NATM construction method, a primary coating is applied by means of spraying mortar or concrete immediately after excavation of the tunnel to prevent falling rock and water leakage in the excavation region. After this, a secondary coating of concrete is applied to stabilizing the tunnel by maintaining tunnel strength. At this time, a waterproofing sheet is installed for the waterproofing purposes, and insulation between the primary coating concrete and the secondary coating concrete, so that leakage of water into the tunnel can be prevented, and so that cracks due to binding of the secondary concrete coating to earth mounds, which might move, can be prevented. Most recently, tunnel excavation has been performed by tunnel boring machines (TBM construction method), and waterproofing sheets are installed for the same objectives.
Installation of this waterproofing sheet involves installation on the primary coating concrete surface by human hands. In particular, there is the problem that it is an operation that is performed on a stand at the ceiling of the tunnel, such that it is dangerous, and there are limitations on movement during the installation operations. In addition, there is the problem that the application surface is the excavation surface, which is uneven, making application after the primary coating difficult to accomplish. Further, because the width of the sheet is narrow (e.g., one to two meters), it is necessary to superimpose numerous waterproofing sheets. The overlapping of the waterproofing sheets requires great effort and is sometimes uneconomical.
There is the further problem that water infiltrates between the waterproofing sheet and the secondary concrete coating due to damage of the sheet by poorly welded components. Also, the irregularities in the excavated surface of the tunnel often defeats the waterproofing capacity of the sheet.
In order to solve these problems, methods for performing waterproofing by spraying an aqueous solution of a polymerizable monomer and forming a waterproofing film was disclosed in Japanese Patent Application (Early Disclosure) No. 61-19683 (1986) and Japanese Patent Application (Early Disclosure) No. 3-137182(1991).
However, there are still problems in that moist surfaces cause poor adhesion, and the film becomes non-uniform due to dripping after spraying. Also, the spraying is foggy, which deteriorates the working environment, and the price is high, making the application uneconomical.
The present inventors conducted various studies of the aforementioned problems. As a result, they discovered a novel tunnel waterproofing construction method in which a rubber emulsion vulcanizable at ambient temperatures is applied by blowing it and forming a film without seams. The film has excellent physical properties and waterproofing capacity, and the method is extremely economical because it avoids dripping and fogging during spray application. It has fewer organic volatile components in comparison with urethane-based compositions; it has no unpleasant odors; and it has excellent workability and waterproofing properties inside the tunnel. Cracks do not develop in the secondary cement concrete coating.
The present invention, specifically, provides a tunnel waterproofing construction method, wherein a primary spray cement concrete coating is spray applied onto a tunnel excavation surface, a rubber emulsion operative to vulcanize at ambient temperature is spray-applied onto the primary spray cement concrete coating, thereby forming a rubber film thereon, and a secondary cement concrete coating is applied onto the rubber film surface.
More particularly, the tunnel excavation surface is made xe2x80x9cnonlandedxe2x80x9d by the primary spray cement concrete coating (in other words, the irregularities of the excavated earth surface are evened out) so that the ambient-temperature vulcanizable emulsion can be spray-applied onto the primary spray cement concrete and thereafter a secondary cement coating can be established thereon.
In further exemplary embodiments, a buffer-water conductive layer is installed on the primary spray cement concrete coating, and the ambient-temperature vulcanizable emulsion is thereafter applied thereon to form a rubber film, whereupon the secondary cement concrete coating may subsequently be established on the rubber film.